In general, multi-function tools include in a pair of cooperable jaws such as plier jaws, and a variety of tools such as screwdrivers, knife blades and files. Multi-function tools may also include a pair of scissors or other pivoted implement (which will hereinafter be referred to generally as "scissors"). Scissors included in multi-function tools typically do not have handle loops configured to receive a human finger to facilitate the operation of the scissor blades. As a result, scissors included in multi-function tools include a spring to bias the blades to the open position. In the open position the cutting surfaces of the blades form an acute angle, such that an item to be cut may be placed between the cutting surfaces.
When not in use, the scissors are typically stored within the handle of the multi-function tool. Conversely, the scissors can be rotated about an axle or pivot out of the handle to an extended or working position. Therefore the spring arrangement must allow for the rotation of the scissors from the extended position to a stored or retracted position within the handle.
Prior art multi-function tools have used two basic spring arrangements to facilitate the biasing of the scissor blades. The first type of arrangement utilizes a spring located in the handle portion of the multi-function tool. The spring biases a fulcrum which in turn biases a working blade relative to a second blade. The spring/fulcrum arrangement is exemplified in the LEATHERMAN MULTI-PURPOSE TOOL PSII.RTM. and the WENGER SWISS ARMY KNIFE.RTM., photographs of which have been filed herewith. The spring/fulcrum arrangement requires both the use of a spring located in the handle portion of the multi-function tool as well as a fulcrum member resulting in additional material cost.
The second type of arrangement utilizes a separate spring element attached to the scissors. In this arrangement a portion of the spring itself biases the handles of the scissors to an open position without the use of a fulcrum member. The open position is defined by the cutting surfaces of the scissor blades being at an acute angle. Several spring types may be used in this second arrangement.
One spring type, which is exemplified in the VICTORINOX.RTM. Swiss Army Knife, utilizes a flat leaf spring having a first end attached to a first scissor handle distal the blade tip and a second end which biases the second scissor handle. This flat spring is positioned between the handles intermediate the blade pivot and the multi-function tool handle. This type of spring is subject to becoming dislodged (thus no longer performing its function), damaged or lost.
Additionally, in this flat spring type, the distance between the multi-function tool handle and the blade pivot must be sufficient to receive the spring. This requires the blade pivot to be further from the tool handle thereby requiring additional storage space in the tool handle and increasing material cost. The LEATHERMAN MULTI-PURPOSE TOOL PSII.RTM. noted above attempted to locate the scissor pivot close to the multi-function tool axle. However, to accomplish this result, the second scissor blade includes two separate portions. This configuration increases material costs and requires additional storage space within the tool handle.
Another type of spring utilized with the second arrangement may be configured as a coil spring mounted about the blade pivot. This spring type is exemplified in U.S. Pat. No. 4,203,208 entitled "BIASED POCKET KNIFE SCISSORS" to Tausendfreundt et al. The coil spring disclosed in the '208 patent is located in a tear shaped pocket in a first blade member. The first end of the coil spring includes a leg extending into an aperture in the second blade. The second end of the coil spring includes a portion which extends tangentially away from the arc of the coil spring and is biased against a side of the tear shaped pocket thereby biasing the blades to an open position.
This coil spring configuration does not, however, easily permit the blades to be located 180 degrees relative to one another for compact storage within the multi-function tool handle. Additionally, the coil spring is exposed and may therefore be contaminated by foreign particles. Further, the spring is compressed when the scissors are retracted in the tool handle. This may result in spring creep which can weaken the spring over time.
It is therefore desirable to provide a multi-function tool including spring biased scissors or other pivoted implement in which the scissors are configured to alleviate the short comings of prior art items discussed above. That is, in which the spring is not subject to damage or loss and does not require a separate fulcrum member, and where the blade pivot is located closer to the multi-function tool handle. Finally, it is also desirable to provide spring biased scissors having a spring that is not biased when the scissors are retracted in the tool handle.